The World Health Organisation has said there are no safe limits for mercury consumption, which can cause brain and kidney damage, memory loss and language impairment.

Switzerland and Norway began pushing a decade ago for such a mercury treaty.

But governments approved exceptions for uses such as measuring devices for which there are no mercury-free alternatives, vaccines where mercury is used as a preservative and products used in religious or traditional activities.

The amount of mercury found in the top 300 feet of the world’s oceans has doubled in the past 100 years, while rivers and lakes hold an estimated 260 tons of mercury previously held in soils.